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Reverse ballistic experiment resembling the conditions in turbine blade off event for containment structures
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.ORCID iD: 0000-0002-5351-9338
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.ORCID iD: 0000-0001-5218-396X
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.ORCID iD: 0000-0001-7074-8960
Number of Authors: 42016 (English)In: Thin-walled structures, ISSN 0263-8231, E-ISSN 1879-3223, Vol. 107, p. 671-677Article in journal (Refereed) Published
Abstract [en]

An experimental technique has been developed which allows loading of heated sheet material under impact conditions with simultaneous measurement of the impact force history. The combined characteristics of impact loading at elevated temperature makes the experiment ideal for validation of models used to simulate the containment structure surrounding aircraft engines. In this paper experimental results for Alloy 718 are presented, a nickel based super alloy commonly used in hot parts of the containment structure. The experimental results are then compared to simulations in order to validate previously calibrated material parameters. The basic principle of the validation experiment is based on reverse ballistics, in which a thin circular specimen with free boundaries impacts the end of an instrumented rod. Using induction heating the specimen is heated to temperatures up to 650 °C and a gun driven by compressed air accelerates the specimens to desired velocity. In the reported work velocities are kept low enough to avoid cracking and thus the study is limited to plastic conditions, even though the technique is applicable also for fracture studies. The free boundaries of the experiment makes numerical modelling and simulation straightforward, making it valuable as a validation tool. All numerical simulations are performed using the commercial finite element code LS-Dyna and plastic behaviour of the material was modelled with the Johnson-Cook material model

Place, publisher, year, edition, pages
Elsevier , 2016. Vol. 107, p. 671-677
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-14178DOI: 10.1016/j.tws.2016.07.002ISI: 000383813200054Scopus ID: 2-s2.0-84982803960Local ID: d87e4938-9599-407f-9604-78c6dbbcdf41OAI: oai:DiVA.org:ltu-14178DiVA, id: diva2:987132
Note

Validerad; 2016; Nivå 2; 20160825 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2025-10-21Bibliographically approved
In thesis
1. Method Development for Characterisation of Superalloy used in Containment Design
Open this publication in new window or tab >>Method Development for Characterisation of Superalloy used in Containment Design
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Metodutveckling för karaktärisering av superlegering med tillämpning i containmentdimensionering
Abstract [en]

Due to the trend of increasing environmental demands put on civil aviation, manufacturersof commercial aircraft engines meet increased pressure to reduce weight. Modernturbofan engines represent up to almost one tenth of an aircraft's total weight, meaning areduction of engine component weight of just 30 kg is estimated to reduce CO2 emissionsby 400 tonnes over the lifetime of a medium sized commercial aircraft. At the sametime turbine casings are required to fully prevent debris to escape in the event of bladefailure, to prevent further damage to critical systems. For new designs to be approvedthe Federal Aviation Regulations (FAR) states that the containment capability of a suggesteddesign solution must be experimentally established, a process associated with highcosts and long lead times. The industry therefore more frequently relies on numericalsimulations as part of all stages in the design process. For simulations to replace theexpensive experiments in nding the nal optimum design regarding weight and safety,the accuracy of the used models have to be improved.This thesis aims to provide increased accuracy in the numerical predictions by developingexperimental procedures to test material close to the operational conditions of thecontainment structure. This is realised by performing experiments at high-strain ratesand elevated temperatures in a high-velocity tensile testing machine combined with aninduction heater. Sheet specimens of varying geometries are loaded in tension to achievedierent stress states for covering dierent failure modes. Furthermore, high-speed photographyand Digital Image Correlation are utilised to track in-plane deformations. Theresulting local deformations are then used to derive the stress-strain hardening relationand the evolution of the stress state from initial loading up to fracture. The obtaineddata are nally used to calibrate strain rate and thermal dependent plasticity and fracturemodels. To validate the calibrated models so-called reverse impact testing was used,where the resulting force of a material sample impacting an instrumented target wasquantied. The experiment was straightforward to model numerically since the specimenies freely without constraints, thereby avoiding complex boundary conditions.The characterisation method was developed and performed on nickel based Alloy 718.This material is known for its high strength and good corrosion resistance at high temperaturesand is therefore commonly used in hot parts of aircraft engines, such as thecontainment structures of the low-pressure part of the engine turbine. All material fortesting and validation was supplied from one single heat and batch, aged using the sameheat treatment conditions, to ensure consistent mechanical properties. The results fromthe characterisation procedure showed that the plastic ow of Alloy 718 is moderatelystrain rate and temperature dependent while the fracture is clearly stress state dependent.

Place, publisher, year, edition, pages
Luleå University of Technology, 2017
Series
Doctoral thesis / Luleå University of Technology, ISSN 1402-1544
National Category
Metallurgy and Metallic Materials Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-62799 (URN)978-91-7583-866-3 (ISBN)978-91-7583-867-0 (ISBN)
Public defence
2017-05-24, A109, LTU, Luleå, 09:00 (English)
Opponent
Supervisors
Funder
Vinnova
Available from: 2017-04-05 Created: 2017-03-30 Last updated: 2025-10-22Bibliographically approved

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Sjöberg, TedSundin, Karl-GustafKajberg, JörgenOldenburg, Mats

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